21-05-2004, 12:27
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#13
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Inactive
Join Date: Jun 2003
Location: Huthwaite, Nottinghamshire
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Posts: 4,536
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Re: Max speed of cable modems?
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Originally Posted by JustAnotherN00b
No, the modems are produced with the capacities of the equipment that they are connecting to in mind, the actual bandwidths available on a single downstream depends on the channel width, modulation type and modulation level in question.
Most cable modems can't sustain anywhere near the transfer rates the uBRs can simply because there was no need for them to, so cheaper less powerful DSPs have been used in their construction.
I'm not aware of any cable modem that can sustain a full 38Mbps down and 10Mbps up (the max capacity on DOCSIS1/1.1 that could be theoretically given to a single modem).
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When I said "The bandwidth available on the UBR cards for both upstream and downstream is far less than the modems are capable of at this moment in time." I was using the fact that many UBRs (using DOCSIS and QAM64) have a downstream limit of around 27 Mbps which becomes nearer 20 Mbps after overheads and an upstream limit of around 2 Mbps.
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